Dribble of oil at prop, usual suspects checked, now puzzled

[IanFS]

Alpha One 1988 attached to Mercruiser V6 1988
Hi guys,
I haven't been able to use the boat this year, weather's been sh*te and people visiting etc. However with a break in the weather, no company and Mrs FS working I bought the boat home from the yard to do some checks etc.
Engine runs fine but after the first run up adjusting the throttle cable etc, I noticed a dribble of oil at the end of the prop and wiped it off. Next run up a small drop or two of emulsified oil at the end of the prop. I took the prop off suspecting a weep from the prop shaft oil seal but nothing, plus nothing in the lower housing.
I replaced the upper seals a few years ago. Drained the oil to check for water emulsion but its clean. Took off the lower housing to check the usual suspects, water pump seal onto drive shaft, also to see if there were any signs of a dribble on the drive shaft. The shaft was covered in soot but no sign of an oil dribble and no signs down the exhaust either. I took off the water pump, but couldn't see any signs of oil leaking from the lower gearcase.
New water pump on order but I'm stumped now.
Any suggestions will be gratefully received.

 

[tank1949]

Alpha One 1988 attached to Mercruiser V6 1988
Hi guys,
I haven't been able to use the boat this year, weather's been sh*te and people visiting etc. However with a break in the weather, no company and Mrs FS working I bought the boat home from the yard to do some checks etc.
Engine runs fine but after the first run up adjusting the throttle cable etc, I noticed a dribble of oil at the end of the prop and wiped it off. Next run up a small drop or two of emulsified oil at the end of the prop. I took the prop off suspecting a weep from the prop shaft oil seal but nothing, plus nothing in the lower housing.
I replaced the upper seals a few years ago. Drained the oil to check for water emulsion but its clean. Took off the lower housing to check the usual suspects, water pump seal onto drive shaft, also to see if there were any signs of a dribble on the drive shaft. The shaft was covered in soot but no sign of an oil dribble and no signs down the exhaust either. I took off the water pump, but couldn't see any signs of oil leaking from the lower gearcase.
New water pump on order but I'm stumped now.
Any suggestions will be gratefully received.

You can buy a pressure testing kit. I suggest purchasing one and using it, or you will always have doubts. Every shaft seal I have seen was dry rotted, but they didn't leak. I guess I was lucky!

 

[IanFS]

You can buy a pressure testing kit. I suggest purchasing one and using it, or you will always have doubts. Every shaft seal I have seen was dry rotted, but they didn't leak. I guess I was lucky!

Can you just pressure test the lower gearcase or do you have to reinstall it to the upper case?

 

[Bondo]

Can you just pressure test the lower gearcase or do you have to reinstall it to the upper case?

Ayuh,..... You just have to plug the passage 'tween the upper, 'n lower,......

Did you fog the 'ell outa the motor last fall,..??
If so, that might explain it,....

 

[Scott Danforth]

check power steering level. if its low, your PS cooler could be leaking

 

[QBhoy]

I’m thinking it’s fogging oil too. If you fogged before lay up. Perhaps even with 2 stroke ? All the best.

 

[kenny nunez]

Look inside the lower seal cavity in the upper unit with about 10 lbs of pressure. You can close off the transfer oil hole with a tapered wood dowel .Quite often the surface of the lower gear is pitted. If so then you will have to break it down and install a “Speedy Sleeve” over the pitted surface.
On the lower if that is where the leak is it just might be the shift shaft bushing. Also sometimes the lower water pump shaft seal is the problem.

 

[jimmbo]

How bad does it smell, the drippings? Gear Oil stinks to High Heaven, while Oil that goes thru the Engine, will smell of Gas and Oil

 

[IanFS]

Ayuh,..... You just have to plug the passage 'tween the upper, 'n lower,......

Did you fog the 'ell outa the motor last fall,..??
If so, that might explain it,....

No Bondo, just the normal fogging.

 

[IanFS]

check power steering level. if its low, your PS cooler could be leaking

Yes Scott the PAS fluid was low during testing, so topped it up, but PAS fluid is red, this looked more green than red. Very interesting diagnosis though, thanks.

 

[IanFS]

Look inside the lower seal cavity in the upper unit with about 10 lbs of pressure. You can close off the transfer oil hole with a tapered wood dowel .Quite often the surface of the lower gear is pitted. If so then you will have to break it down and install a “Speedy Sleeve” over the pitted surface.
On the lower if that is where the leak is it just might be the shift shaft bushing. Also sometimes the lower water pump shaft seal is the problem.

Kenny, the Shift Shaft seal (which showed through the tell tale hole) and the Shift Shaft Bushing (with Gen II bush)was replaced a few years ago, they both look dry.

 

[IanFS]

How bad does it smell, the drippings? Gear Oil stinks to High Heaven, while Oil that goes thru the Engine, will smell of Gas and Oil

Yes Jimmbo you are so right, it does stink. So the first dribble was fairly clear greeny colour about the size of a finger nail, the second dribble was a little emulsified as few drops of oil in the residual water from the cooling.

 

[IanFS]

Thank you so much to all of you for your help.
I'm trying to follow Tanks advice by trying to source a pressure tester. There are quite a few available in the UK but none with a 3/8 16 thread. I can find a 3/8 18 hose adapter which might work with a foot pump, but nothing with a 3/8 16 thread.
I so wish we had stayed Imperial sizes instead of silly Metric!!!!

 

[KJM]

Do you have a pump for putting gear oil into your lower drive? The screw in end of that tube might work. I once rigged up something like that with a 12v car tire pump that had pressure guage and the end of the oil refill tube. Don't over pressurize the lower unit with air or you risk damaging good seals!

 

[ROY WILLIAMS]

Thank you so much to all of you for your help.
I'm trying to follow Tanks advice by trying to source a pressure tester. There are quite a few available in the UK but none with a 3/8 16 thread. I can find a 3/8 18 hose adapter which might work with a foot pump, but nothing with a 3/8 16 thread.
I so wish we had stayed Imperial sizes instead of silly Metric!!!!

I was the outdrive MR the 7-10 psi on the 24 hrs very good ... Then the pressure is dropping , then the dish soap spraying is and the bubbles in that area ...

 

[IanFS]

Do you have a pump for putting gear oil into your lower drive? The screw in end of that tube might work. I once rigged up something like that with a 12v car tire pump that had pressure gauge and the end of the oil refill tube. Don't over pressurize the lower unit with air or you risk damaging good seals!

Yes I have a a gear oil pump, but thought it may not be strong enough to hold pressure, although it is only 10-12lbs psi. what a great idea, thanks. I've got a bike pump that goes up to 70psi so it should work.
Thank you.

 

[KJM]

I had my lower unit off at the time and immersed it in a big tub of water and waited for the bubbles. My problem ended up being the shift shaft seal.

 

[IanFS]

Wow, my goodness, what a great idea.

 

[jimmbo]

I had my lower unit off at the time and immersed it in a big tub of water and waited for the bubbles. My problem ended up being the shift shaft seal.

Okay for Pressure Testing, but not good when pulling a Vacuum

 

[nola mike]

Yes I have a a gear oil pump, but thought it may not be strong enough to hold pressure, although it is only 10-12lbs psi. what a great idea, thanks. I've got a bike pump that goes up to 70psi so it should work.
Thank you.

I have a length of tubing with a schrader valve on one end and gear lube fitting on the other and use a bike pump to pressurize. no need to make it complicated.